A precise polish process for polishing the surface of a material is required in, for example, optical disk substrates, a magnetic disks, glass substrates for flat panel displays, clock boards, camera lenses, glass material used for various lenses and crystal material for filters or the like for optical components, substrates of a silicon wafer or the like for semiconductors, and insulated films, metal layers and barrier layers or the like formed in each process for manufacturing semiconductor devices. The surfaces of these materials require high accuracy polishing. Therefore, for example, polishing agents have been generally used, using silica, zirconium oxide and alumina or the like alone or in combination of two or more kinds as polish particles. Referring to a form of the polishing agent, for example, a slurry-like polishing agent obtained by dispersing the polish particles in a fluid, a polishing agent obtained by curing the polish particles with a resin and other binder, and a polishing agent obtained by adhering and/or fixing only particulates of the polish particles on the substrate surface of fiber, resin and metal or the like with the binder have been generally used.
A silica polishing slurry using particularly silica particulates as the polish particles has been widely used as the polishing slurry for precision polish for a wiring formation or the like in the manufacture of a semiconductor integrated circuit (hereinafter, referred to semiconductor) because of little scratch generation of a surface to be polished. However, since the polishing speed of the silica polishing slurry is slow, attentions have been recently focused on a cerium oxide polishing slurry containing cerium oxide having a fast polishing speed (for example, see Japanese Patent Application Laid-Open Nos. 2000-26840 and 2-371267). However, the cerium oxide polishing slurry has a problem of generating more scratches as compared with the silica polishing slurry.
Though the cerium oxide polishing slurry has been used for glass polish for many years, it has been necessary to avoid impurity contamination as much as possible so as to apply the cerium oxide polishing slurry to the planarization of the semiconductor. Then, rare earth materials are refined once, and a high purity cerium oxide is obtained via a cerium salt. As the cerium salt, cerium carbonate, cerium oxalate and cerium nitrate or the like are used. The polishing slurry for semiconductor planarization has been manufactured by dispersing the cerium oxide obtained by calcining and grinding these cerium salts.
Though it has been presumed that the scratches generated in the polish process relate to the particle diameter of the polishing slurry, quantitive evaluation results have been seldom obtained. It has been said that the scratches are decreased when a filter in the manufacturing process is used and coarse particles are removed in the case of the silica polishing slurry. In this case, the relationship between the physical properties of the polishing slurry after filtration and the scratches is not apparent.
Though it has been considered that the cerium oxide polishing slurry has a larger mean particle diameter than that of the silica polishing slurry and has a great content of the coarse particles, since a measurement technique having high sensitivity has not been established, the reliability of the measurement results has been inadequate. Therefore, the relationship between the coarse particles and the scratches is merely conceptually understood, and an effective specific measure has been deficient.
For example, in a paragraph (0020) of Japanese Patent Application Laid-Open No. 10-154673, the maximum particle diameter is measured by a laser diffraction type particle size distribution meter, and Japanese Patent Application Laid-Open No. 10-154673 discloses that one having 1 μm or more is not contained. Thus, the scratches have been prevented by conventionally measuring using a laser diffraction type particle size distribution meter of Mastersizer (trade name, manufactured by Malvern Instruments Ltd.) or the like to reduce the maximum particle diameter of the particle.
However, even if the maximum particle diameter detected by the particle size distribution meter is reduced, the prevention of the scratches is limited, so that responding to integration of the semiconductor these days has been difficult.
Consequently, the present inventor has conducted earnest studies of the cause. As a result, the present inventor found that, in fact, particles of 3 μm or more considered not to exist in the measuring method using the particle size distribution meter exist in a very small quantity which is undetectable, and affect the scratches.
On the other hand, high integration of the semiconductor has been advanced, and processing size of wiring or the like is miniaturized to 100 nm. As the processing has been miniaturized, the defective reduction of the scratches or the like has been still strongly required, and the polishing slurry satisfying all of the polishing speed, planarization and scratch reduction has been required.